Picture transmission apparatus



Get. 17, 1939- G. N. OGLOBLINSKY 2,176,225

PICTURE TRANSMISSION APPARATUS Filed Sept. 28, 1935 3 Sheets-Sheet 1 I zg -n mww GPAZOPY/M 06208107810; pa-msz 7, 1939- G. N. OGLOBLINSKY 2,176,225

PICTURE TRANSMISSION APPARATUS Filed Sept. 28, 1935 3 Sheets-Sheet 2 jl l l l l l il will 0 17, 3 e. N. OGLOBLINSKY 2, 5

PICTURE TRANSMISSION APPARATUS Filed Sept. 28, 1935 5 Sheets-Sheet 5 ".H'PI'I I I IW Ina/671,507

Patented Oct. 17, 1939 zusgzs 2.176.225 7 PICTURE 'rnansmssron arrana'rus Gregory N.

iingswood, N. .L, b

Oglobllnsky, deceased, late of Coly Vladimir administrator, Philiid K. Zworykin,

elphla, Pm, aseignor to Radio Corporation of Americana corporation of Delaware Application September 2a. 1935,, Serial Names-r l 12 Claims; (Cl. l'lsl-z) "The invention-relates to picture transmission apparatus andparticularly to cathode ray tubes designed to generate picture signals.

An object of the invention is to provide an improved method of and means for producing picture signals.

i A further object of the; invention is to provide an improved ,method of. and'means for taking picturesignals from elements of a mosaic structure or the like.

' A further object of the invention is to provide an improved means for utilizing the phenomenon of secondary electron emission in producing'pic-- ture signals.

A still further object of' the invention is to provide an improved method of and .means for utilizing the phenomenon of secondary electron emission in picture transmitting tubes or the like.

A still further object of the invention is to"v 0 provide an improved cathode ray picture transmitter tube and/or associated circuit.

Otherobjects, features and advantages of the invention will appear from the following 'descrip tinn taken in connection with the accompanying drawings in' which Figur'e llis a schematic and circuit diagram of one embodiment of the invention;.

Figure 2 ma perspective view of certain'electrode structure shown in Figure 1;

Figure 2a is a view taken Figure 2;.

Figure 3 is a' schematic and circuit diagram 7 of another embodimentof the invention;

I Figure 4 is a' perspective view of-certain electrode structure shown in Figure 3;

Figure a schematic .and circuit-diagram of still another embodiment or the invention; and

Figure 6 is a'perspective view of certain .electrode structure shown in Figure 5. Referring to Figure 1 there is shown a cathode ray transmitter-tube comprising-a highly evacuated envelope I having. an electron gun therein, consisting of an indirectly heated cathode 2, a control electrode 3 and a first anode 4.

focusing the cathode ray. It is.usually preferred to maintain the second anode 6 at a higher posi tive potential than the first anode 41in order to further accelerate the electrons; However, as

indicated on the drawings, the second anode 6- maybe at' a lower potential thantheflrst anode and good focusing of theelectron beam obtained by properly selecting the ratio of anode voltages. A direct'current voltage may be applied to the anode 4 from any suitable source, such as a batin cross section on A second anode 6 is provided for electrostatically tery 1. while the second anode 6 is maintained at ground potential. The control" electrode 8 may be maintained at the same potential as the cathode 2.

' Preferably. a portionoi the innersurtace ol- 1 the envelope I is provided with a metallic coating 8 which maintained anode. This arrangement prevents 'thedeiiecting coils 9 from inducing interfering signals into the picture signal output circuit.

Any suitable means such as a pair of deflecting coils 9 is provided for deflecting the cathode ray isconnected to ground whereby it is in a direction at right anglesto the plane of the.

- The electrode structurewhich is scanned-by the cathode rayv for the-purpose of producing picture; signals and which is shown more clearly in Figures 2 and 2a includes a large number of metallic pins ll, nickel pins for example, which .are mounted in any suitable insulating support such as a glass block II. It will be noted that the pins II are insulated from each other and do not have any direct current connection to any part 01' the tube structure or circuit.- Each pin corresponds to a picture element ofv the picture at the same potential as the second 7 being transmitted, there-being. of course,a much 4 a larger number of pins in an actual embodiment of the-invention than indicated on the'drawings.

-In front or the pins- II and supported from the glass block l2 there is a collector'electrode I! which in the particular embodiment illustrated is a conductor'bent into the shape 01' a rectangle.- Instead oi.being in this particular form. the collector electrode I! may be in the i'orm of a plate having aslit-like opening cut therein.

In front 01' the collector electrode I 3 and supported from the glass block I! there is a shield ll which. preferably'is of conducting material which is, maintained at means-of, a suitable connection In the shield I4 opposite each pin ll there is sage of the, cathode ray therethrough to strike the pin: II and at the same time to prevent the cathode ray from striking the collector electrode an opening I! of such size as to permit the pasground potential by I3. It will be, evident that as the cathode rayis deflected along the row of pins II it passes through the openings I I to strike'the pins successively without striking the collector electrode l3.. 'As-each pin- H is struck by the cathode ray, :it emits secondary electrons which are collected by the electrode H, as will be more completely described-hereinafter. 1

' the drawings or it may be made either slightly positive or slightly negative with respect to ground by adjusting the tap 22 on the battery 23. Voltage variations appearing across the output resistor 2| are impressed upon the input circuit of a suitable amplifier 24.

The apparatus above described is suitable for transmitting pictures from a motion-picture film indicated at 26. In front of the film 28 there is a shield 21 having a narrow slit'28 extending across the width of the film and parallel to the row of pins II. The film 26 .is illuminated by light passing through suitable condensing lenses 2!! and an image of the picture at the slit 28 is projected upon the photosensitive, screen I8 by means of a suitable optical system indicated at 3!.

Vertical scanning of the picture is effected by running the picture film 2B continuously while the cathode ray is being deflected horizontally and at right angles to the movement of the film. It has been found that the secondary electrons emitted by the pins ll vary in, accordance with the shading of the picture elements. -'I'herefore the signal appearing in the output of the ampiifier 24 is a picture signal which may be transmitted to reproduce the picture at a-sutiable picture or television receiver. It is believed that the operation of the transmitter tube is substantially as follows:

The image of the picture projected upon the photosensitive screen causes the screen to emit photo-electrons depending in number upon the intensity of light at a particular point on the screen. Thus, a pin opposite a brightly lighted point on the screen will receive more photo-electrons than a pin opposite a dimly illuminated point and it will become more negatively charged. As each pin is bombarded by the electrons from the cathode ray it will emit secondary electrons which will move over to the collector electrode. The number of secondary electrons which will move over to the collector electrode will depend upon the potential difference between the pin and the collector electrode. Therefore, if the collector electrode is at ground potential, for example, the

more negative a pin the greater will be the num-- ber of secondary electrons moving over to the electrode. This variation in the number of secondary electrons reaching the collector electrode is, of course, the picture current and represents a positive picture.

As will be more clearly understood from the description of the circuit shown in Figure 3 which follows, thescreen I 8 may be maintained at a positive potential with respect to ground providing the ends of the pins which face the screen are made photosensitive. In that case, there is no object in having the screen itself photosensitive.

In Figure 3 the tube structure, except for the pin or mosaic structure and associated electrodes, is substantially the same as shown in Figure 1, like parts in the two figures being indicated by Preferably the pins 32 extend beyond the honeycomb structure 34 both at the front and at the back. It has been found that in some cases im- 1 proved results may be obtained if mica sheets 36 and 31 are placed at the front and back of the honeycomb structure, respectively, with the pins 32 extending therethrough.

A collector electrode 38 is positioned in front of the pins 32, this collector taking the form of a metallic plate having an opening 39 therein opposite each pin. A metallic shielding electrode 4| is positioned in front of the collector electrode 38, the shielding electrode having a row of openings 42 therein each of which is positioned in line with a pin and its corresponding opening 39 in the collector electrode. The openings 42 in the shielding electrode 4! are smaller than the openings 39 in the collector electrode whereby electrons in the main electron beam or cathode ray may pass through the openings in the shielding electrode II to the pins 32 without striking the collector electrode 30. Thus, as in the structure shown in Figure 1 only the secondary electrons from the pins 32 reach the collector electrode 38.

The collector electrode 38 is preferably connected through an output resistor 43 to ground whereby picture signals may be taken 011 the resistor 43 by means of any suitable amplifier 44.

As in the case of the apparatus shown in Figure 1, a photosensitive screen 46 may be positioned on the back side of the pins 32 and maintained at a negative potential with respect to ground by means of a battery 41. When operated in this way, the screen 48 may have a negative potential of from 10 volts to 'l0 volts. Preferably, however, the ends of the pins 32 facing the screen 46 are made photosensitive while the-screen is merely a metallic screen which is not photosensitive. In this case, the screen 48 is maintained at a positive potential with respect to ground and acts as a collector of photo-electrons. The positive screen potential is not critical, potentials of from 45 volts to volts having been found satisfactory. 1

In the case of the preferred embodiment just described, the operation is substantially as follows:

An image of the picture at the slit 28 is pro- .iected upon the photosensitive ends of the pin: 32 whereby they emit more or less photo-electrons depending upon the shading of the picture elements, The more electrons emitted by a pin, th more positive it becomes. Therefore, the num' ber of secondary electrons which pass from eacl pin to the collector electrode 38 depends upon the shading of the picture elements and the fiov of current through the output resistor .43 is th' picture signal which represents a negative pic ture.

In the embodiment of the invention shown 11 Figure 5, the tube structure for generating th cathode ray is the same as that shown in Figure i In the two figures like parts are indicated by th same reference numerals.

In the specific embodimentof the inventio: shown in Figure 5, instead of employing a singi line of pins, a complete mosaic of pins is em have been J'ected thereon to release ployed whereby an outdoor scene or the like may be picked up by a camera. and the picture transmitted by projecting the image upon a photosensitivescreen or upon the ends of the pins which made photosensitive.

The mosaic pin structure, which is also shown in Figure 6, comprises a honeycomb structure 5| which may be made from nickel ribbon, glass beads 52 which are inserted in the honeycomb openings, and metallic pins 53 which are supported in the glass beads 52. The construction of this honeycomb mosaic is substantially the same as that of the honeycomb structure shown in Figure 4.

In front of the mosaic pins 53 are positioned collector and shielding plates 54 and 56, respec tively, the collector plate 54 having comparatively large openings therein which are located opposite the pins 53. The shielding plate 56 has a corresponding number 01 smaller openings which are positioned opposite the collector plate openings and in line with these openings and the pins. The collector plate 54 and shielding plate 56 correspond to the collector and shielding electrodes 38 and 52, respectively, shown in Figures 3 and 4, and their functions are the same.

The honeycomb structure 5| and the shielding plate 56 are preferably connected to the metallic coating 8 and to ground. The collector plate or electrode 54 is connected through an output resistor 51 either directly to ground or through a battery 58 inserted for the purpose of maintaining the collectorelectrode positive with respect to ground. Picture signal is taken off the output.

resistor 51 by means of the amplifier 59.

If desired, the ends of the pins 53 on the back side of the mosaic may be made photosensitive and a positive screen for collecting photoelectrons placed adjacent thereto whereby the tube may be operated as described in connection with Figure 3. In that case, an image of the pic'- ture to be transmitted is projected upon the light-sensitive ends of the pins.

In the particular embodiment illustrated, however, a photosensitive screen 6| is placed opposite the back side of the mosaic whereby an image of. the picture 52 to be transmitted may be prophoto-electrons. The structure of this screen may be the same as that of the screen l8 shown in Figure 1. A fine mesh metallic screen 63 is positioned between the mosaic and the photosensitive screen BI and maintained at a positive potential with respect to the photosensitive screen by means of a battery 64 or the like, for the purpose of accelerating the photo-electrons and projecting them towards the mosaic. Since the photosensitive screen 6| is located some distance from the mosaic, a magnetic focusing coil 66 is provided which 'causes the photo-electrons leaving a particular point on the photosensitive screen 6| to move over to a corresponding point on the mosaic.

If desired, the accelerating screen 63 and the focusing coil 66 may be omitted and the photosensitive screen 6| placed so close to the mosaic that'focusing of the photo-electrons is unnecessary.

In the. several embodiments of the invention described above the electron beam velocity is not critical. A beamvelocity of from 200 volts to 500 volts was found to be satisfactory.

From the foregoing description it will be apparent that various other modifications may be made in the invention without departing from the spirit and scope thereof andit is desired therefore that onry such limitations shall be imposed thereon as are necessitated by the prior art and set forth in the appended claims.

What is claimed is:

1. In a transmitter tube, means for generating a beam of electrons, a mosaic of elements each electrically insulated whereby it may receive and retain a charge and each adapted to emit secondary electrons, elements to receive a charge corresponding to the shading of a picture element, means for causing said beam to scan saidelements whereby secondary electrons are emitted, and means including a collector electrode positioned out of thepath of said beam for collecting said secondary electrons and supplying them to a picture signal circuit.

means for causing each of said 2. The invention according to claim 1 characterized in that said collector electrode'has at leastone opening therein, said electrode being positioned out of the region traversed by said beam and being so positioned that said beam passes through said opening to strike at least one of said elements.

3. In an electron tube, means for generating a beam of electrons, a mosaic of elements each electrically insulated whereby it may receive and retain a charge and each adapted to emit secondary electrons, means for causing each of said elements to receive a charge corresponding to the shading of a picture element, means for causing said beam to scan said elements whereby secondary electrons are emitted, an electrode positioned to be bombarded by said secondary e1ectrons but not by the electrons in said beam, and a signal output device connected between said electrode and ground.

4. In an electron tube, a plurality of elements each adapted to receive an electric charge corresponding to the shading of a picture element and each adapted to emit secondary electrons, means for causing said elements to receive said charges, means for generating a beam of electrons and directing it towards saidelements, said beam generating means including an electrostatic focusing electrode, means for deflecting said beam and causing it to scan said elements whereby secondary electrons are emitted, and means including a collecting electrode out of the path of said beam for collecting said secondary electrons and sup plying them to a utilization circuit;

5. The inventionaccording to claim 4 characterized in that said focusing electrode is connected to ground.

6. The invention according toclaim 4 characterized in that shielding 'means is provided between said'beam deflecting means and said elements, said shielding means being in the form of a metallic coating on the-inner surface of the electron tube envelope and being connected to ground.

7. In an electron tube, means for generating a beam of electrons, a mosaic of elements each electrically insulated whereby it may receive and retain a charge and each adapted to emit secondary electrons, means for causing each of said elements to receive a charge corresponding to the shading of a picture element, means for scanning said elements by said beam and thereby producing secondary electrons which vary in quantity in accordance with said charges, an electrode for collecting said last mentioned secondary electrons, and an output impedance unit'connected between said collecting means and ground.

8. In a transmitter tube, means for generating a beam of electrons, said means including an elec trostatic focusing electrode. a plurality of elements each adapted to receive an electric charge corresponding to the shading o! a picture element and each adapted to emit secondary electrons, means for causing said elements to receive said charges, means for causing said beam to scan said elements whereby secondary electrons are emitted, and means for collecting said secondary electrons and supplying them to a picture signal output circuit, said collecting means comprising an electrode having an opening therein, said electrode being positioned between said beam generating means and said elements and out of the path of said beam whereby the beam passes through said opening.

9. The invention according to claim 8 characterized in that said electrode is substantially in the form of a ring. 7 W V v 10. In a transmitter tube, means for generating a beam of electrons, at least one row of elements, each element being adapted to receive a charge corresponding to the shading of a picture element and each adapted to emit secondary electrons, means for projecting an image of said picture toward the back side of said elements, means including an electrode positioned between said elements and said projecting means for causing each element to receive a charge corresponding to said shading, means for causing said beam to scan the front side of said elements whereby they emit secondary electrons, means for collecting said electrons and supplying them to a picture signal circuit, said collecting means comprising a collector electrode positioned adjacent to the front side of said pins, and a shielding element so positioned between said beam generating means and said collector electrode that the beam is prevented from striking the collector electrode.

11. In combination, means for producing a beam of (electrons, a mosaic of elements each adapted to receive a charge and adapted to emit secondary electrons, a photosensitive screen, means for projecting an optical image upon said screen whereby photo-electrons are released, an acceleration screen positioned between said photosensitive screen and said mosaic, means for maintaining said accelerating screen positive with respect to said photosensitive screen whereby said photo-electrons are projected against the back side of said mosaic, means for establishing a focusing field between said mosaic and said accelerating electrode such that photo-electrons leaving points on said photosensitive screen reach corresponding points on said mosaic, means for scanning said mosaic on the front side by said beam, whereby said elements emit secondary electrons, and means for collecting said secondary electrons and supplying them to a picture circuit.

12. In combination, means for generating'a beam of electrons, a mosaic of elements each electrically insulated whereby it may receive and retain a charge and each adapted to emit secondary electrons, means for causing each of said elements to receive a charge corresponding to the shading of a picture element, means for causing said beam to scan said elements whereby secondary electrons are emitted, an electrode positioned adjacent to said elements and out of the region traversed by said beam whereby it collects said secondary electrons, a connection between said electrode and ground, said connection inciuding an impedance unit, an amplifier tube having an input circuit, and means for coupling said input circuit across said impedance unit. VLADIMIR K. ZWORYKIN, Administrator of the Estate .0! Gregory N.

Oaloblinsky, Deceased. 

